1. Field of the Invention
The present invention relates to a radiographic apparatus, a radiographic method, a program, a computer-readable storage medium, a radiographic system, an image diagnosis aiding method, and an image diagnosis aiding system.
2. Description of the Related Art
In recent years, systems that employ large-area semiconductor image sensors to radiograph an object have been developed. Such a system has practical advantages, as compared with a conventional radiographic system based on silver salt films, in that an image can be recorded over an extremely large range of radiation dose. More specifically, X-rays with an extremely wide dynamic range are read as electric signals using a photoelectric converter, and the electric signals are converted into digital signals. The digital signals are processed to output a high-quality radiograph as a visible image on a recording material such as a photosensitive film material, or to a display apparatus such as a CRT display. Accordingly, an adequate radiograph is obtained even if the dose of radiation exposure fluctuates somewhat.
In radiography using semiconductor image sensors, dynamic imaging of the lung during breathing, instead of the conventional diagnostic imaging primarily based on still imaging, is expected to provide new pathologic information. The imaging of the lung during breathing is such that the lung is dynamically imaged from when it is expanded to when it is contracted, preferably for one cycle of breath including an expanding period and a contracting period of the lung.
In conventional still imaging, guidance for keeping a patient still (by which is meant, whatever is done toward keeping the patient still) has been performed not by a machine but by a technologist. This is because it is more difficult to achieve appropriate timing of exposure, using machine guidance.
In imaging of the lung during breathing, as opposed to still imaging of the lung with the breath held, it is difficult to acquire image data of a breathing cycle (breathing period) accurately in phase (e.g., to acquire image data from start of inhaling to end of exhaling) within dynamic images that are continuously captured. This is because even if a patient is instructed to start inhaling upon start of imaging, some amount of delay—an amount that depends on the patient—occurs. In particular, the delay is prominent in aged patients or patients with weakened physical strength since these patients are unable to respond quickly. When a doctor diagnoses images that have been thus taken, if the phase of breathing at start of image display differs from patient to patient, a diagnosis method cannot be fixed and diagnosis will take more time.
This variation in phase at the start of image display can be reduced by controlling timing of the start and end of imaging, using a sensor for monitoring breath. However, this requires an instrument to be attached to a patient, which adds labor and time to the procedure. Furthermore, when imaging is performed over a breathing cycle, including inhaling and exhaling, during approximately ten seconds, it is difficult for a technologist suitably to control an inhaling phase and an exhaling phase to be five seconds each while monitoring the patient. Accordingly, it was necessary to guide a breathing cycle of the patient and to control imaging (e.g., X-ray irradiation) in accordance with the guide.